package rsa;

public class HexUtil {

  private static final char[] DIGITS_LOWER = {'0', '1', '2', '3', '4', '5',
      '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
  private static final char[] DIGITS_UPPER = {'0', '1', '2', '3', '4', '5',
      '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

  /**
   * 16进制转byte数组
   *
   * @param data 16进制字符串
   * @return byte数组
   * @throws Exception 转化失败的异常
   */
  public static byte[] hex2Bytes(final String data) throws Exception {
    final int len = data.length();

    if ((len & 0x01) != 0) {
      throw new Exception("Odd number of characters.");
    }

    final byte[] out = new byte[len >> 1];

    // two characters form the hex value.
    for (int i = 0, j = 0; j < len; i++) {
      int f = toDigit(data.charAt(j), j) << 4;
      j++;
      f = f | toDigit(data.charAt(j), j);
      j++;
      out[i] = (byte) (f & 0xFF);
    }
    return out;
  }

  /**
   * bytes数组转16进制String
   *
   * @param data bytes数组
   * @return 转化结果
   */
  public static String bytes2Hex(final byte[] data) {
    return bytes2Hex(data, true);
  }

  /**
   * bytes数组转16进制String
   *
   * @param data bytes数组
   * @param toLowerCase 是否小写
   * @return 转化结果
   */
  public static String bytes2Hex(final byte[] data, final boolean toLowerCase) {
    return bytes2Hex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
  }


  /**
   * bytes数组转16进制String
   *
   * @param data bytes数组
   * @param toDigits DIGITS_LOWER或DIGITS_UPPER
   * @return 转化结果
   */
  private static String bytes2Hex(final byte[] data, final char[] toDigits) {
    final int l = data.length;
    final char[] out = new char[l << 1];
    // two characters form the hex value.
    for (int i = 0, j = 0; i < l; i++) {
      out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
      out[j++] = toDigits[0x0F & data[i]];
    }
    return new String(out);
  }

  /**
   * 16转化为数字
   *
   * @param ch 16进制
   * @param index 索引
   * @return 转化结果
   * @throws Exception 转化失败异常
   */
  private static int toDigit(final char ch, final int index)
      throws Exception {
    final int digit = Character.digit(ch, 16);
    if (digit == -1) {
      throw new Exception("Illegal hexadecimal character " + ch
          + " at index " + index);
    }
    return digit;
  }

  /*
   * 16进制字符串转字符串
   */
  public static String hex2String(String hex) throws Exception {
    String r = bytes2String(hexString2Bytes(hex));
    return r;
  }

  /*
   * 字节数组转字符串
   */
  public static String bytes2String(byte[] b) throws Exception {
    String r = new String(b, "UTF-8");
    return r;
  }

  /*
   * 16进制字符串转字节数组
   */
  public static byte[] hexString2Bytes(String hex) {

    if ((hex == null) || (hex.equals(""))) {
      return null;
    } else if (hex.length() % 2 != 0) {
      return null;
    } else {
      hex = hex.toUpperCase();
      int len = hex.length() / 2;
      byte[] b = new byte[len];
      char[] hc = hex.toCharArray();
      for (int i = 0; i < len; i++) {
        int p = 2 * i;
        b[i] = (byte) (charToByte(hc[p]) << 4 | charToByte(hc[p + 1]));
      }
      return b;
    }
  }

  /*
   * 字符转换为字节
   */
  private static byte charToByte(char c) {
    return (byte) "0123456789ABCDEF".indexOf(c);
  }

  /*
   * 字符串转16进制字符串
   */
  public static String string2HexString(String s) throws Exception {
    String r = bytes2HexString(string2Bytes(s));
    return r;
  }

  /*
   * 字节数组转16进制字符串
   */
  public static String bytes2HexString(byte[] b) {
    String r = "";

    for (int i = 0; i < b.length; i++) {
      String hex = Integer.toHexString(b[i] & 0xFF);
      if (hex.length() == 1) {
        hex = '0' + hex;
      }
      r += hex.toUpperCase();
    }

    return r;
  }

  /*
   * 字符串转字节数组
   */
  public static byte[] string2Bytes(String s) {
    byte[] r = s.getBytes();
    return r;
  }


}
